Effect of Dodecylbenzenesulfonic Acid as an Asphaltene Dispersant on the W/O Emulsion Stabilized by Asphaltenes and Paraffin Wax

Abstract

Dodecylbenzenesulfonic acid (DBSA) is injected into wellbores as an asphaltene dispersant to alleviate asphaltene deposition problems. The addition of DBSA will change the dispersion of asphaltenes in the crude oil, affecting the wax precipitation property of the crude oil as well as the adsorption behavior of asphaltenes at the oil–water interface, thus significantly altering the W/O emulsion’s stability. In order to provide better theoretical guidance for oil–water separation in oilfield gathering and production processes, in the paper, the effects of DBSA concentration (from 0 to 500 ppm) on the emulsions’ stability containing both asphaltenes and paraffin wax and the mechanism were systematically investigated at two different temperatures (30 and 15 °C) based on the wax precipitation and rheological properties of the model crude oil, the oil–water interface adsorption properties, and the macroscopic and microscopic properties of the emulsion. The outcomes demonstrated that the test temperature had a highly substantial impact on the model emulsion. The main element affecting the stability of the emulsion at 30 °C (above the wax appearance temperature (WAT)) was the interfacial structure’s strength. The low-temperature flowability of the oil phase primarily controlled the process of emulsion stabilization at 15 °C (below the WAT). Furthermore, we speculate that the wax crystals could precipitate on the surface of the emulsified droplets, which also facilitated emulsion stability at 15 °C. Combining the above experimental observations, the mechanism of DBSA concentration affecting the emulsion stability was proposed, which would contribute to solving the issues in the emulsion breaking and dewatering process of crude oil emulsions.